A wireless communication system has been extensively developed to provide various types of communication services such as a voice, data, and the like. In general, a wireless communication system is a multi-access system supporting communication between multiple users by sharing available system resources (bandwidth, transmission power, and the like). Examples of multi-access systems include a CDMA (code division multiple access) system, an FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, an SC-FDMA (single carrier frequency division multiple access) system, and the like.
A general wireless communication system largely considers only a single carrier although bandwidths for uplink and downlink are set to be different. A carrier is defined by a center frequency and a bandwidth. A multi-carrier system uses a plurality of carriers having a bandwidth smaller than an overall bandwidth.
3GPP LTE (long term evolution) based on 3GPP (3rd Generation Partnership Project) TS (Technical Specification) Release 8 is a potential next-generation mobile communication standard.
The 3GPP LTE system supports only one bandwidth (i.e., one carrier) among {1.4, 3.5.10, 15, 20}MHz. In order to support an overall bandwidth of 40 MHz, a multi-carrier system uses two carriers each having 20 MHz bandwidth, or uses three carriers having 20 MHz bandwidth, 15 MHz bandwidth, and 5 MHz bandwidth, respectively.
The multi-carrier system can guarantee lower backward compatibility with an existing system and highly enhance a data rate through multiple carriers.
In the single carrier system, a control channel and a data channel are designed based on a single carrier. Here, the use of an existing channel structure as it is in multiple carriers in order to maintain compatibility with the single carrier system will possibly be ineffective.
Thus, a channel structure that is able to support the multi-carrier system is required.